Historically, wireless networks have been homogeneous across several dimensions: radio access technology, macro versus small cell or femto cell, and hub and spoke versus a mesh network. Each of these wireless communication networks has its strengths and weaknesses. Fixed cellular macro networks suffer from dead spots, storm related outages, impeded coverage in inclement weather, difficulty providing in-building coverage, dropped calls on hand-overs, susceptibility to jamming, and so forth. Small cell access points have limited range. And mobile ad hoc networks are good for a small team working on a joint mission, but historically these networks have been stand-alone.
Wireless multimedia services are typically delivered through a series of macro base stations placed on towers or other strategic locations. This architectural layout applies to civilian and public safety networks. Irrespective of the end-user, the demand being placed on macro networks is exceeding macro network capabilities. On the public safety side, interoperability among different public safety departments and ensuring reliable coverage in hard-to-reach zones, such as in-building, have also been major challenges for the towns and municipalities that provide wireless multimedia services to public safety officials.
Recently, civilian operators have been finding ways to enhance cellular network coverage. For example, about 75% of all pro sports teams have added distributed antenna systems (“DAS”) to their venues as a way of reducing the burden placed on the cellular macro network servicing the arena during game time. Although DAS enabled venues increase capacity, they are expensive to install and operate, and they do not provide mobility. DAS systems do not add any intelligence to the network. Instead, they simply act as repeaters.
Stepping back, cellular networks are inherently pre-planned networks. They do not form in an ad hoc fashion like a military ad hoc network. Although military ad hoc networks have the advantage of being ad hoc, their flexibility is limited to data channels within the same frequency band. In addition, military ad hoc networks do not integrate into existing cellular networks. Rather, they operate like independent islands.
When femto cells or repeaters are added to cellular networks, their integration is also preplanned. Femto cells provide cellular access using an Ethernet backhaul. Although they are moveable, they are nonetheless tied to a wired backhaul. Additionally, when a femto cell is moved, the operator of the femto cell must reconfigure the reintegration of the femto cell back into the existing network. In some femto cells, this reintegration can be accomplished by inputting the GPS coordinates of the femto cell. In other femto cells, interference mitigation can be accomplished by identifying any additional cellular base stations within range of the femto cell.
Repeaters are essentially amplifiers. Repeaters take the input signal, amplify it, and send it out. They do not change the frequency of the input signal, the protocol of the input signal, the duplexing scheme of the input signal and so forth.
Looking forward, industry leaders believe that heterogeneous networks will become more ubiquitous because they increase capacity. Heterogeneity, by its very definition, means being diverse in character or content. In wireless communication networks of the prior art, this could mean adding a small cell to a macro network, the heterogeneity being combining a small cell with a macro cell.
Some of the challenges of integrating small cells into a macro cellular network include: backhauling the traffic to the cell site, which can be expensive and inefficient; finding a site for outdoor small cells; and managing a network filled with macro cells and small cells. This is heterogeneity at a base station level.
In another example, military radios may have channel diversity in that they could assign different channels to users within a network, each channel having a different frequency. This could be seen as frequency heterogeneity or diversity. But the frequencies assigned within this network would all be within a particular frequency band. And so managing this network is fairly straightforward because there is one owner for the frequency band and therefore only one set of management principles governing the frequency band.
While these examples show some heterogeneity in the prior art, there is a need for furthering the concept of heterogeneity because by doing so, network capacity increases markedly. Heterogeneity can and should exist beyond the base station level. Specifically, the prior art lacks heterogeneity at the network level, that is combining various networks together such as an ad hoc cellular network with a fixed cellular network. There is therefore a need for managing ad hoc cellular networks in such a way as to seamlessly integrate them into and enhances the coverage of existing fixed cellular networks. There is also a need for dynamically leveraging myriad frequencies, protocols, duplexing schemes.